RFID device tester and method

ABSTRACT

Multiple RFID devices may be tested by moving a sheet, roll, or web of the devices in conjunction with a test apparatus having multiple RFID device testers, so that the RFID devices to be tested are each spatially static with regard to one of the RFID device testers for a period of time, during which testing may be performed. The device testers may be arrayed along the circumference of a circular test wheel or roller, or may be arrayed along the perimeter of a flexible belt. The coupling between the RFID devices and the RFID device testers may be capacitive. By utilizing short-range capacitive coupling, difficulties caused by simultaneous activation of multiple RFID devices may be reduced or avoided.

This is a continuation-in-part of U.S. application Ser. No. 10/367,515,filed Feb. 13, 2003, and a continuation-in-part of InternationalApplication No. PCT/US04/04227, filed Feb. 13, 2004, and published inEnglish as WO 2004/072892. Both of the above applications are herbyincorporated by reference in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the field of radio frequency identification(RFID) tag and label detection systems, and to methods of detecting andtesting RFID tags and labels.

2. Description of the Related Art

Radio frequency identification (RFID) tags and labels (collectivelyreferred to herein as “devices”) are widely used to associate an objectwith an identification code. RFID devices generally have a combinationof antennas and analog and/or digital electronics, which may include forexample communications electronics, data memory, and control logic. Forexample, RFID tags are used in conjunction with security-locks in cars,for access control to buildings, and for tracking inventory and parcels.Some examples of RFID tags and labels appear in U.S. Pat. Nos.6,107,920, 6,206,292, and 6,262,692, all of which are herebyincorporated by reference in their entireties.

As noted above, RFID devices are generally categorized as labels ortags. RFID labels are RFID devices that are adhesively or otherwise havea surface attached directly to objects. RFID tags, in contrast, aresecured to objects by other means, for example by use of a plasticfastener, string or other fastening means.

RFID devices include active tags and labels, which include a powersource, and passive tags and labels, which do not. In the case ofpassive tags, in order to retrieve the information from the chip, a“base station” or “reader” sends an excitation signal to the RFID tag orlabel. The excitation signal energizes the tag or label, and the RFIDcircuitry transmits the stored information back to the reader. The“reader” receives and decodes the information from the RFID tag. Ingeneral, RFID tags can retain and transmit enough information touniquely identify individuals, packages, inventory and the like. RFIDtags and labels also can be characterized as to those to whichinformation is written only once (although the information may be readrepeatedly), and those to which information may be written during use.For example, RFID tags may store environmental data (that may bedetected by an associated sensor), logistical histories, state data,etc.

One difficulty associated with RFID devices is the need to testoperation of such devices as part of the manufacturing or fabricationprocess. In fabrication of RFID devices, the devices may be formed on asheet or roll of material, closely spaced apart. In traditional methodsof activating, reading, and/or detecting RFID devices, an antenna isused to send radio frequency (RF) fields over a relatively long range,that is, over intervening free space. When such methods are applied totesting closely-spaced RFID devices, it is difficult to test a singleRFID device, since the RF field interacts with several devicessimultaneously, and the various RFID devices may interact with oneanother.

In addition, it will be appreciated that lost-cost methods of readingRFID devices are desirable.

From the foregoing it will thus be appreciated that improvements in RFIDdevice testing and reading would be desirable.

SUMMARY OF THE INVENTION

According to an aspect of the invention, multiple RFID devices may betested by moving a sheet, roll, or web of the devices in conjunctionwith a test apparatus having multiple RFID device testers, so that theRFID devices to be tested are each spatially static with regard to oneof the RFID device testers for a period of time, during which testingmay be performed. The device testers may be arrayed along thecircumference of a circular test wheel or roller, or may be arrayedalong the perimeter of a flexible belt. The coupling between the RFIDdevices and the RFID device testers may be capacitive.

According to another aspect of the invention, a method of testing aplurality of radio frequency identification (RFID) devices, includes thesteps of: substantially continuously moving a web of that includes theRFID devices; at the same time, substantially continuously moving atleast a portion of a test apparatus that includes plural RFID devicetesters such that at least some of the RFID device testers maintainstatic relative spatial relationships with respective of the RFIDdevices for respective periods of time; and for each of the RFIDdevices, testing the RFID device with one of the RFID device testerswhile the RFID device is in a static spatial relationship with the oneof the RFID device testers.

According to yet another aspect of the invention, a method of testing aradio frequency identification (RFID) device, includes the steps of:capacitively coupling an RFID device tester to an antenna of the RFIDdevice; generating an outgoing signal from the RFID device tester; usingthe outgoing signal to power the RFID device; generating a return signalin the RFID device; and detecting a return signal, via a reader that ispart of the tester. The RFID device tester includes coupling elementselectrically connected to the reader. The antenna of the RFID deviceincludes antenna elements. The capacitively coupling includes aligningthe coupling elements with respective of the antenna elements. Thecoupling elements are part of a roller. The RFID device is part of aroll material. The aligning includes bringing the portion of the rollmaterial having the RFID device into alignment with the couplingelements as the roller rotates.

According to still another aspect of the invention, a radio frequencyidentification (RFID) device tester includes: a reader; a pair ofelectrically-conductive coupling elements; a pair of transmission lineselectrically connecting respective of the coupling elements to thereader; and a resistor connected to both of the transmission lines,between the reader and the coupling elements. The coupling elements arepart of a roller.

According to an aspect of the invention, an RFID device tester iscapacitively coupled to an RFID device, in order to provide power fromthe tester to the device, and to receive a signal from the device to thetester.

According to another aspect of the invention, an RFID device testerprovides power to an RFID device to be tested, by sending an outgoingpower signal that is at a frequency other than the resonant frequency ofthe antenna of the RFID device.

According to yet another aspect of the invention, an RFID device testerhas conductive coupling elements for capacitively coupling to antennaelements of an RFID device.

According to still another aspect of the invention, an RFID devicetester has hoop-shaped conductive coupling elements.

According to another aspect of the invention, an RFID device test systemhas multiple testers operatively coupled together for testing a web ofdevices having rows of devices, with multiple devices in each row.According to an embodiment of the invention, the multiple testers may bein a staggered configuration, rather than being in a line in thedirection of the rows.

According to a further aspect of the invention, a method of testing aradio frequency identification (RFID) device, includes the steps of: 1)capacitively coupling an RFID device tester to an antenna of the RFIDdevice; 2) generating an outgoing signal from the RFID device tester; 3)using the outgoing signal to power the RFID device; 4) generating areturn signal in the RFID device; and detecting a return signal, via areader that is part of the tester.

According to a still further aspect of the invention, a radio frequencyidentification (RFID) device tester includes a reader; a pair ofelectrically-conductive coupling elements; a pair of transmission lineselectrically connecting respective of the coupling elements to thereader; and a resistor connected to both of the transmission lines,between the reader and the coupling elements.

According to another aspect of the invention, in a combination of aradio frequency identification (RFID) device and an RFID device tester,the RFID device includes an antenna having a pair of antenna elements;and a chip operatively coupled to the antenna. The RFID device testerincludes a reader; and a pair of electrically-conductive couplingelements electrically connected to the reader. The antenna elements areeach capacitively coupled with respective of the coupling elements,thereby forming a pair of capacitors.

According to yet another aspect of the invention, a method of testing aradio frequency identification (RFID) device includes the steps of:shifting an optimum operating frequency of the device from a naturalresonant frequency to a shifted resonant frequency; and reading thedevice at a frequency other than the natural resonant frequency.

According to still another aspect of the invention, a method of testinga radio frequency identification (RFID) strap includes the steps of:capacitively coupling an RFID device tester to conductive leads of theRFID strap; generating an outgoing signal from the RFID device tester;using the outgoing signal to power the RFID strap; generating a returnsignal in the RFID strap; and detecting a return signal, via a readerthat is part of the tester.

According to a further aspect of the invention, a test system, fortesting a web containing multiple rows each having multiple RFIDdevices, includes: a proximity sensor for detecting the rows of RFIDdevices; a plurality of testers arrayed to test the multiple RFIDdevices of each of the rows; and a computer operatively coupled to theproximity sensor and the plurality of testers. The computer receivessignals from the proximity sensor and controls operation of testers.

According to a still further aspect of the invention, a method oftesting a web of RFID devices, the web including multiple rows eachhaving multiple of the RFID devices, includes the steps of: detectingone of the rows of the web by a proximity sensor; and testing the RFIDdevices of the row by use of respective testers that are operativelycoupled to the proximity sensor.

To the accomplishment of the foregoing and related ends, the inventioncomprises the features hereinafter fully described and particularlypointed out in the claims. The following description and the annexeddrawings set forth in detail certain illustrative embodiments of theinvention. These embodiments are indicative, however, of but a few ofthe various ways in which the principles of the invention may beemployed. Other objects, advantages and novel features of the inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the annexed drawings, which are not necessarily to scale:

FIG. 1 is schematic side view of an RFID device tester capacitivelycoupled to an RFID device, in accordance with the present invention;

FIG. 2 is a top view of the RFID device tester and RFID device of FIG.1;

FIG. 3 is a circuit diagram illustrating the capacitive coupling of theRFID device tester and the RFID device of FIG. 1;

FIG. 4 is a top view illustrating parts of an embodiment of the RFIDdevice tester of FIG. 1, which shifts the optimum operating frequency ofan RFID device;

FIG. 5 is a top view illustrating parts of another embodiment of theRFID device tester of FIG. 1, which shifts the optimum operatingfrequency of an RFID device;

FIG. 6 illustrates an alternate embodiment RFID device tester,capacitively coupled to an RFID device, in accordance with the presentinvention;

FIG. 7 illustrates an RFID device tester testing a roll of RFID devicesin a roll-to-roll process, in accordance with the present invention;

FIG. 8 is a view illustrating another embodiment RFID device tester inaccordance with the present invention;

FIG. 9 is a view illustrating yet another embodiment RFID device testerin accordance with the present invention;

FIG. 10A illustrates the RFID device tester of FIG. 9 as part of aroll-to-roll process;

FIG. 10B illustrates an alternative tester system for testing a web ofRFID devices;

FIG. 10C illustrates another alternative tester system for testing a webof RFID devices;

FIG. 10D illustrates yet another alternative tester system for testing aweb of RFID devices;

FIG. 11 is a top view of an RFID device test system in accordance withthe present invention;

FIG. 12 is a top view of another RFID device test system in accordancewith the present invention;

FIG. 13 is an oblique view of an RFID device test system in accordancewith the present invention;

FIG. 14 is a plan view of the system of FIG. 13;

FIG. 15 is a block diagram of one embodiment of an RFID test system;

FIG. 16 is a block diagram of another embodiment of an RFID test system;

FIG. 17 is a block diagram of yet another embodiment of an RFID testsystem; and

FIG. 18 is a timing diagram of part of the operation of an RFID devicetest system in accordance with the present invention.

DETAILED DESCRIPTION

An RFID device tester includes coupling elements for capacitivelycoupling a reader to an RFID device to be tested. The reader may powerthe RFID device by sending an outgoing signal, such as an outgoing ACpower signal, which may be rectified and/or reflected by the RFIDdevice, if the RFID device is operating properly. The outgoing signalmay have a frequency that is different from the resonant frequency of anantenna of the RFID device. A reader in the RFID device tester detectsthe reflected and/or transmitted signal to confirm proper operation ofthe RFID device. The RFID device tester may be used as part of aroll-to-roll process, to individually test RFID devices on a roll ofmaterial. By utilizing short-range capacitive coupling, difficultiescaused by simultaneous activation of multiple RFID devices may bereduced or avoided.

In one particular aspect, multiple RFID devices may be tested by movinga sheet, roll, or web of the devices in conjunction with a testapparatus having multiple RFID device testers, so that the RFID devicesto be tested are each spatially static with regard to one of the RFIDdevice testers for a period of time, during which testing may beperformed. The device testers may be arrayed along the circumference ofa circular test wheel or roller, or may be arrayed along the perimeterof a flexible belt. The coupling between the RFID devices and the RFIDdevice testers may be capacitive.

Referring initially to FIGS. 1 and 2, illustrated is an RFID devicetester 10 for testing or otherwise reading an RFID device 12. The testerincludes a reader 14, and a pair of coupling elements or couplers 16 and18 that are electrically coupled to the reader 14. The coupling elements16 and 18 are electrically-conductive elements in any of a wide varietyof suitable configurations. The coupling elements 16 and 18 may beplaced on a dielectric substrate layer 20. In addition, the tester 10may include a terminating resistor or load 24 that is connected betweenthe coupling elements 16 and 18. As described in greater detail below,the terminating resistor 24 may function to restrict the strength ofsignals from the coupling elements 16 and 18 to the reader 14. Asuitable power supply 26 may be used to power the reader 14.

The RFID device 12, which may be a label or a tag, or a part of a labelor a tag, has an antenna 30, and a chip 32 coupled to the antenna 30.The chip 32 may include any of a variety of suitable electroniccomponents, such as the circuitry described above for modulating theimpedance of the RFID device 12. The antenna 30 may be a dipole antennahaving a pair of antenna elements 36 and 38 on opposite sides of thechip 32. Alternatively, the antenna 30 may have another layout. Theantenna elements 36 and 38 may be mounted on a dielectric substrate 40of the RFID device 12. The dielectric substrate 40 may be part of asheet of dielectric material, such as a roll of dielectric material,upon which other RFID devices are formed. The other RFID devices may besubstantially the same as, or alternatively may be different from, theRFID device 12. More specifically, the dielectric substrate may have aplurality of RFID devices closely spaced together.

Making reference now also to FIG. 3, the RFID device tester 10 and theRFID device 12 are capacitively coupled together, to transfer powerand/or signals between the RFID device tester 10 and the RFID device 12.The coupling elements 16 and 18 are operatively coupled to the antennaelements 36 and 38, respectively. This operative coupling is produced byorienting the RFID device tester 10 and the RFID device 12 such that thecoupling elements 16 and 18 of the RFID device tester are substantiallyopposite the antenna elements 36 and 38 of the RFID device 12, as isillustrated in FIGS. 1-3. With such a relative orientation, a portion 46of the dielectric substrate layer 20 is between the coupling element 16and the antenna element 36, and another portion 48 of the dielectricsubstrate layer 20 is between the coupling element 18 and the antennaelement 38. The coupling element 16, the antenna element 36, and thedielectric portion 46 thus function as a first capacitor 50, with thecoupling element 16 and the antenna element 36 being plates of thecapacitor 50, and the dielectric portion 46 being the dielectric of thecapacitor 50. Similarly, the coupling element 18, the antenna element38, and the dielectric portion 48 functions as a second capacitor 52.

Once the RFID device tester 10 and the RFID device 12 are capacitivelycoupled together, electrical power and/or signals may be transferredbetween the two. The reader may send an outgoing signal, such as anoutgoing AC signal, along transmission lines 56 and 58 coupling thereader 14 with the coupling elements 16 and 18. The capacitors 50 and 52allow transmission of the outgoing AC signal from the coupling elements16 and 18 to the antenna elements 36 and 38. AC power received by theantenna elements 36 and 38 may be rectified by the chip 32, for instanceby transistors and/or diodes that are part of the chip 32, to produce DCpower to run the chip 32.

The power may be used by the chip 32 to send a return signal via theantenna elements 36 and 38. It will be appreciated that the sending ofthe return signal may be a passive process, rather than activetransmission of a return signal by the RFID device 12. As one example,circuitry in the chip 32 may be used to modulate impedance of the RFIDdevice 12. As another example, the RFID device 12 may reflect theincident signal back to the tester 10.

It will be appreciated that the RFID device 12 either may be a passivedevice that automatically responds to an incident signal, or may be anactive device that only responds to incident signals conforming tocertain protocols. The RFID device 12 may also have other components,such as its own power supply.

It will be further appreciated that the functioning of the RFID device12 may be substantially the same as if incident energy was provided by along-range RF field, rather than by capacitive coupling. Alternatively,the functioning of the RFID device 12 may be different, depending uponhow the incident energy is provided to it.

The return signal generated by the RFID device 12 is transmitted fromthe antenna elements 36 and 38 to the coupling elements 16 and 18, viathe capacitors 50 and 52. The return signal is then forwarded to thereader 14 along the transmission lines 56 and 58. The terminatingresistor 24 may function to prevent excessively powerful signals fromreaching the reader 14, and perhaps causing damage to the reader 14.

The reader 14 is able to interpret the return signal received from theRFID device 12 to confirm proper function of all or part of the RFIDdevice 12, such as correct functioning of the antenna 30 and/or the chip32. The confirming of proper functioning may include merely detectingthe presence of the RFID device 12, such that if the RFID device 12 isdetectable at all, functioning of the RFID device 12 is acceptable, andthe RFID device 12 passes the test. Alternatively, the test may involveevaluation of the return signal received from the RFID device 12, forexample to determine if the return signal conforms to one or moreparameters or ranges of parameters. It will be appreciated that othertests of operation of the RFID device 12 may be employed, for examplediagnosing faults of the RFID device 12 or otherwise qualitativelyevaluating performance of the RFID device 12.

The outgoing AC power signal sent out by the reader 14 and the returnsignal generated by the RFID device 12 have been described above forclarity as separate signals, one sent out by the reader 14, and theother received by the reader 14. In actuality, it will be appreciatedthat the signals may in fact be superimposed upon one another, in thatthe reader 14 perceives a superposition of the outgoing signal and thereturn signal. Therefore the interpretation of the return signal by thereader 14 may involve a comparison between the outgoing signal and thesignal perceived by the reader 14, a superposition of the outgoingsignal and the return signal.

The RFID device tester 10, which capacitively couples to the RFID device12, advantageously allows short-range coupling between tester 10 andRFID device 12. The RFID device 12 may be part of a sheet or roll havingmany RFID devices thereupon, and by using short-range capacitivecoupling between the RFID device tester 10 and the RFID device 12,better testing of the RFID device 12 may be accomplished, compared totesters coupling to RFID devices via RF fields sent over free space. Onereason for the advantage of the capacitively-coupling RFID device tester10 is that the short-range capacitive coupling is less prone to provideenergy to other RFID devices on the same roll or sheet. By reducing orlimiting the providing of energy to RFID devices other than the RFIDdevice 12 to be tested, there is better discrimination in the testing,and thus improved testing of the RFID device 12.

Appropriately selection of the frequency of the outgoing signal from thetester 10 may allow further reduction in undesired coupling to RFIDdevices other than the RFID device 12 that is being tested. Inexplaining this further, it will be useful to define a natural resonatefrequency of the antenna 30 as the frequency at which the antenna 30best receives energy from an external RF field, and at which it bestsends energy, when not located in close proximity to the RFID devicetester 10. This natural resonant frequency is the frequency at which anantenna impedance of the antenna 30 is the complex conjugate of a chipimpedance of the chip 32. The resonant frequency is also referred toherein as the optimum operating point or optimum operating frequency ofthe RFID device 12. It will be appreciated that the resonant frequencyof the antenna 30 may be highly dependent on the configuration of theantenna 30.

One advantage of the RFID device tester 10, which capacitively couplesto the RFID device 12, is that the outgoing power signal from the reader14 of the RFID device tester 10 may be at a frequency that is differentfrom the natural resonant frequency of the antenna 30 of the RFID device12 (different from the natural optimum operating point of the RFIDdevice 12). By having the outgoing power signal at a different frequencyfrom the natural resonant frequency for the antenna 30 of the RFIDdevice 12, longer-range coupling may be minimized of the outgoingsignals to RFID devices other than the desired RFID device 12 to betested. This is because antennas of the RFID devices are lesssusceptible to receive significant amounts of power at frequenciesdifferent from the resonant frequency of the antenna 30. Further, havingthe outgoing power signal at a different frequency than the naturalresonant frequency of the antenna 30 may reduce cross-coupling betweenthe various antennas of various RFID devices on the same roll or sheet.

Coupling between the RFID device tester 10 and the RFID device 12 willitself alter the resonant frequency of the antenna 30 (the optimumoperating frequency). This is because bringing the tester 10 into closeproximity relative to the RFID device 12 alters the environment aroundthe RFID device 12. One or more dielectric elements 60 (FIG. 1) and oneor more electrically-conducting elements 62 (FIG. 1) of the RFID devicetester 10 may thereby be introduced by the tester 10 into theenvironment perceived by and interacting with the RFID device 12 that isbeing tested. The dielectric elements 60 and the conducting elements 62may be referred to as “shifting elements,” since they function to shiftor change the optimum operating frequency of the RFID device 12. Asillustrated in FIG. 1, the dielectric elements 60 may include thedielectric substrate layer 20, and the conductor elements 62 may includethe coupling elements 16 and 18. Alternatively or in addition, there maybe other dielectric elements 60 and/or conductor elements 62, the latterof which may include metallic conductors. The location, size, and/orconfiguration of the dielectric elements 60 and/or the conductorelements 62 may be selected so as to produce a desired shift in theresonant frequency of the antenna 30.

FIGS. 4 and 5 show illustrative examples of parts of RFID device testers10 with additional dielectric elements 60 and/or conductor elements 62for shifting or altering the resonant frequency of the antenna 30 of theRFID device 12. In FIGS. 4 and 5 the parts of the RFID device 12 areshown somewhat offset from corresponding parts of the RFID device tester10 for illustration purposes.

FIG. 4 shows parts an embodiment of the RFID device tester 10 thatincludes additional dielectric elements 60 a and 60 b that are next tothe coupling elements 16 and 18. The dielectric elements 60 a and 60 bare placed over or opposite respective portions 36 a and 38 b of theantenna elements 36 and 38 of the antenna 30 of the RFID device 12. Asshown, the dielectric elements 60 a and 60 b are further from the chip32 of the RFID device 12, although it will be appreciated that othersuitable configurations may be utilized.

The dielectric elements 60 a and 60 b function to load the antenna 30and increase the effective length of the antenna elements 36 and 38 ofthe antenna 30. By an increase in effective length, what is meant isthat the resonant frequency or optimum operating frequency of the RFIDdevice 12 is decreased.

The dielectric elements 60 a and 60 b may be made of a high K dielectricmaterial, such as a suitable ceramic material. Examples of suitablematerials are barium tetra titanate and titanium oxide.

Turning to FIG. 5, parts of an embodiment of the RFID device tester 10is shown that has additional electrically-conducting elements 62 a and62 b, separate from the coupling elements 16 and 18, that are in closeproximity to the antenna elements 36 and 38 of the antenna 30 of theRFID device 12. The conducting elements 62 a and 62 b are capacitivelycoupled to the antenna elements 36 and 38, increasing the effectivelength of the antenna elements. The resonant frequency or optimumoperating point of the RFID device 12 is thereby decreased.

Although the configuration of the conducting elements 62 a and 62 b inFIG. 5 results in a decrease in the resonant frequency or optimumoperating point of the RFID device 12, it will be appreciated thatdifferently configuring the conducting elements 62 a and 62 b relativeto the RFID device 12 may result in an increase in the resonantfrequency or optimum operating point of the RFID device 12.

The shift in resonant frequency or optimum operating point caused by thedielectric elements 60 or the conducting elements 62 is localized, inthat the dielectric elements 60 a, 60 b and/or the conducting elements62 a, 62 b may be configured to shift the frequency of only a singleRFID device 12, while leaving the optimum operating point of adjacentRFID devices large unaffected.

It will appreciated that the number and configuration of the dielectricelements 60 a and 60 b and the conducting elements 62 a and 62 b may bevaried, and may be optimized for selected antenna configurations and/orfor a desired testing frequency, for example.

The shift in the resonant frequency of the antenna 30, caused bybringing the RFID device 12 and the RFID device tester 10 together, mayaid in operatively isolating the RFID device 12 from other RFID devicesthat may be nearby. By operatively isolating the RFID device 12, it maybe easier to test the RFID device 12 without encountering undesiredresults due to activation or interference from other RFID devices thatare not presently being tested. Since the RFID device 12 to be testedmay be closer than other RFID devices to the dielectric elements 60 andthe conducting elements 62, resonant frequency shifts of the other RFIDdevices may be substantially reduced in magnitude or avoided altogether,when compared with the resonant frequency shift of the RFID device 12 tobe tested. Put another way, the shift in resonant frequency occasionedby the dielectric elements 60 and/or the conducting elements 62 may besubstantially or largely limited to a single RFID device, the RFIDdevice 12 to be tested.

As an example, the dielectric elements 60 and/or the conducting elements62 may be suitably configured so as to shift an antenna having anoptimum operating frequency of 915 MHz to an optimum operating frequencyof 2450 MHz.

It will be appreciated that the above-described concept of shift optimumoperating frequency of the RFID device 12 is but one example of abroader concept. More broadly, testing may be accomplished by shiftingthe optimum operating frequency of one or more RFID devices, and thentesting RFID device(s). The device(s) tested may be (as described above)one or more RFID devices that have had their optimum operating frequencyshifted. Alternatively, testing may be performed on one or more deviceswith unshifted frequencies (normal, typical, or usual frequencies), withother untested RFID devices having frequencies shifted.

It will further be appreciated that different optimum operatingfrequency shifts may be provided to different RFID devices to be tested.Varying the frequency shift for different RFID devices may facilitatetesting multiple RFID devices simultaneously.

In addition, it will be appreciated that the RFID device tester 10 mayhave multiple parts, with for example the dielectric elements 60 and/orthe conducting elements 62 separate from other parts of the tester 10.

The tester operating frequency of the RFID device tester 10 may beselected so as to provide sufficient energy to activate the RFID device12 that is being tested, and avoiding providing substantial amounts ofenergy to other RFID devices that may otherwise produce signalsinterfering with test results. As suggested by the above discussion, thetester operating frequency may be different from the natural resonantfrequency of the antenna 30, and/or may be substantially the same as thenew resonant frequency of the antenna 30 (the resonant frequency of theantenna 30 as shifted due to its proximity to the RFID device tester10).

Alternatively, the tester operating frequency may be selected from abroad range of suitable RF frequencies for operatively coupling thetester 10 and the RFID device 12. The RF frequencies utilized may begreater than or less than the antenna natural frequency and/or the newantenna resonant frequency (shifted due to the proximity of the tester10 to the RFID device 12). It will be appreciated, however, that RFfrequencies that stray too far from the new antenna resonant frequency(shifted optimum operating frequency) may be unsuitable. For example,there may be a lower limit for suitable RF frequencies due to increasesin impedance of capacitive paths, for a given coupling area, asfrequencies are reduced. This increase in impedance may make it moredifficult to send power into the chip. As another example of a reasonfor a lower frequency limit, internal rectifiers in the chip 32 may havean integrating filter after them, to aid in creating the DC power supplyto run the chip 32. If the frequency of the incident RF energy receivedfrom the tester 10 is too low, the filter may be unable to adequatelysmooth the rectified waveform output from the rectifiers. The result maybe an unacceptable DC power supply for the chip 32.

There also may be an upper limit for suitable RF frequencies for theoperating frequency for the tester 10. As frequency increases, rectifierefficiency within the chip 32 decreases, reducing the fraction of inputenergy that is converted to DC energy to run the chip 32. Another reasonfor an upper limit for suitable operating frequencies is that the chip32 may have a large input capacitance that acts as a voltage divider inconjunction with the coupling capacitors 50 and 52. As frequency of theincoming signal is increased, it therefore becomes more difficult tocoupled power into the RFID device 12.

According to a specific example, the coupling elements 16 and 18 may be3 mm×20 mm plates. The separation distance between the coupling elements16 and 18 and the antenna elements 36 and 38 may be about 0.2 mm.Assuming that the relative dielectric constant of the interveningdielectric material is 3, the capacitance of each of the capacitors 50and 52 is 7.97 pF.

The coupling elements 16 and 18 are shown in FIG. 1 as approximately thesame size as the corresponding antenna elements 36 and 38. It will beappreciated, however, that coupling elements 16 and 18 may be larger orsmaller than the antenna elements 36 and 38 (for example as shown inFIG. 2).

It will be appreciated that the RFID device tester 10 may have othercomponents in addition to those shown and described above. For example,the outgoing AC power signal may include sending signals along thetransmission lines 56 and 58 that are 180 degrees out of phase with eachother. A balance transformer may be utilized to produce the out of phaseRF signals.

As another example, the RFID device tester 10 may have a matchingnetwork between the reader 14 and the transmission lines 56 and 58. Thematching network may be utilized to change the impedance of the signaltransmitted from the reader 14 to the transmission lines 56 and 58. Forexample, the characteristic impedance of the reader 14 may be on theorder of 50 ohms, while the desired impedance of the field set up by thetransmission lines 56 and 58 may be 200 ohms. The matching network maybe used to shift the impedance of the signal from the reader 14 to thedesired impedance for the transmission lines 56 and 58.

FIG. 6 shows an alternative relative orientation between the RFID devicetester 10 and the RFID device 12, in which the RFID device 12 isinverted as compared to the orientation shown in FIGS. 1 and 2, anddescribed above. In the configuration shown in FIG. 6, portions of thedielectric substrate 40 of the RFID device 12 act as the dielectric ofthe capacitors 50 and 52. The dielectric layer 20 of the RFID devicetester 10 (FIG. 1) may thus be omitted.

As a further alternative, it will be appreciated that an air gap may beused as the dielectric for the capacitors 50 and 52. The RFID devicetester 10 and/or the RFID device 12 may have structures or otherelements to maintain a repeatable air gap between the coupling elements16 and 18 of the RFID device tester 10, and the antenna elements 36 and38 of the RFID device 12.

Turning now to FIG. 7, the RFID device tester 10 may be utilized in aroll-to-roll process to test a plurality of RFID devices 12 that areparts of or are on a roll material 70. The tester 10 may be fixed inlocation, with the various RFID devices 12 being tested one at a time asthey move past the tester 10. The roll material 70 may be appropriatelydriven to move the RFID devices 12 past the tester 10. The RFID devices12 may move continuously past the tester 10, or alternatively each ofthe RFID devices 12 may pause to be tested as it passes under the RFIDdevice tester 10. The RFID device tester 10 may be coupled to a computeror other device for recording results of the testing of the various RFIDdevices, and for enabling the devices to be matched up with their testresults.

The roll-to-roll process illustrated in FIG. 7 may be part of or may beoperatively coupled with a larger roll-to-roll process for fabricatingRFID devices. It will be appreciated that roll-to-roll fabricationprocesses for producing RFID devices may include many well-known steps,such as depositing various layers (e.g., adhesive layers, metal layers,and/or printable layers), modifying the layers (e.g., selectivelyremoving parts of a metal layer to create an antenna), and/or depositingvarious components (e.g., a chip). Further details regardingroll-to-roll fabrication processes for RFID devices may be found in U.S.Pat. No. 6,451,154, which is hereby incorporated by reference in itsentirety.

Another alternative configuration for the RFID device tester 10 is shownin FIG. 8, wherein the coupling elements 16 and 18 and dielectric layers20 a and 20 b covering the coupling elements 16 and 18, are parts of thewheels 76 and 78. Thus, the coupling elements 16 and 18 and thedielectric layers 20 a and 20 b may be annular or hoop-shaped. Thecoupling elements 16 and 18 may be coupled to the reader 14 in a mannersimilar to the coupling described above with regard to otherembodiments.

The RFID device tester 10 shown in FIG. 8 may be rolled over astationary sheet or roll of material having a plurality of RFID devices12 to be tested. Alternatively, the RFID device tester 10 may be keptstationary as the sheet or roll of RFID devices 12 moves, in contactwith the wheels 76 and 78. The device tester 10 may advantageously helpmaintain a consistent distance between the coupling elements 16 and 18of the tester 10, and the antenna elements 36 and 38 of the RFID device12.

Yet another alternative configuration for the RFID device tester 10 isshown in FIGS. 9 and 10A. The tester 10 shown in FIG. 9 allows fortesting of RFID devices 12 in a roll-to-roll process, with the RFIDdevices 12 being in a fixed relationship in close proximity to a pair ofcoupling elements for a minimum amount of time, even while the rollmaterial 70 is constantly in motion. In addition, the tester 10 shown inFIG. 9 advantageously enables testing of multiple RFID devices 12 at onetime.

As shown in FIG. 9, the tester 10 includes a roller 80 that has multiplepairs of coupling elements 16 a, 18 a; 16 b, 18 b; and 16 c, 18 cthereupon or therein, along or on an outer surface 82 of the roller 80.The roll material 70, with various RFID devices 12 thereupon, windsaround the roller 80. The outer surface 82 of the roller 80 moves at thesame speed as the roll material 70, such that the roll material 70 doesnot substantially slip relative to the roller 80. It will be appreciatedthat the RFID device 12 thus maintains its position relative thecorresponding pair of coupling elements 16 c and 18 c, for a certaincoupling time period (as long as the part of the roll material 70 withthe RFID device 12 is in contact with the outer surface 82 of the roller80). The RFID device 12 may thus be suitably coupled to a correspondingpair of coupling elements 16 c and 18 c, for a coupling time period.

The rotation speed of the roller 80 and the roll material 70 may beselected such that the coupling time is sufficient to allow for testingof the RFID device 18. It will also be appreciated that, for a givenrotation speed, use of a larger diameter roller results in a longercoupling time.

The various coupling elements 16 a-c and 18 a-c are coupled to a reader14 having multiple outputs, via a rotary joint 86. It will beappreciated that pairs of coupling elements may be evenly spaced aroundthe outer surface 82 of the roller 80, at a spacing corresponding to thespacing of the RFID devices 12 on the roll material 70. Having multiplepairs of coupling elements on the roller 80 may enable testing ofmultiple RFID devices 12 simultaneously, which advantageously speeds thetesting process.

Referring to FIG. 10A, the roll material 70 may move from a supply roll90 to a take-up roll 92. Rollers 96 and 98 may be used in conjunctionwith the roller 80 to maintain a portion of the roll material 70 againstthe roller 80. The roll material 70 may be moved from the supply roll 90to the take-up roll 92 by one or more suitable motors driving one ormore of the rollers 80, 96, and 98, and/or one or both of the rolls 90and 92.

The configuration of the rolls 90 and 92, and the rollers 80, 96, and92, shown in FIG. 10A, is an illustration of one of a large variety ofsuitable configurations, which may include other rollers, mechanisms,and/or devices.

It will be appreciated that an RFID tester in the configuration employedin FIG. 9 may have coils as part of its coupling elements 16 a-c, 18a-c, and thus may be able to test RFID devices that are nothigh-frequency devices. For example, the tester may be configured totest 13.56 MHz RFID devices. Thus the coupling between the pairs ofcoupling elements 16 a-c, 18 a-c may be capacitive, or alternatively maybe by another suitable mechanism.

It will be appreciated that the various embodiments of the RFID devicetester 10 may also be employed as readers, to detect the presence ofRFID devices 12 or to otherwise receive information from RFID devices12.

It will further be appreciated that a capacitively coupling RFID devicetester/reader such as described above may have a variety of suitableconfigurations. For example, the RFID device tester/reader may havesuitably-shaped slots or other openings for receiving RFID devices to betested or read, or for receiving objects having RFID devices attached orotherwise coupled thereto.

As noted above, the RFID device may be a part of a tag or label. Forexample, the RFID device may be a RFID strap having a chip attached toconductive leads that do not function as a conventional antenna.Examples include an RFID strap available from Alien Technologies, andthe strap marketed under the name I-CONNECT, available from PhilipsElectronics. Thus the various embodiments of the tester may be suitablefor use in testing a roll of RFID straps, with conductive elements ofthe RFID tester placed in proximity to the conductive leads of the RFIDstrap.

FIG. 10B shows still another alternate embodiment for the RFID devicetest system (also referred to as a test apparatus) in which a staticrelationship is maintained for a period of time between individualtesters and devices to be tested. The test system 100 shown in FIG. 10Bincludes a rotatable test wheel 101 with a number of individual RFIDdevice testers 102 arrayed circumferentially around a perimeter of thetest wheel 101. The spacing of the device testers 102 is configured tocorrespond to the spacing of RFID devices 104 on a web 105 of devices(alternatively referred to herein as a roll of devices). As the testwheel 101 rotates and the web 105 moves along with the test wheel 101,the RFID devices 104 in a portion of the web 105 maintain their spatialrelationship with the testers 102 for a period of time, until thatportion of the web 105 separates away from the test wheel 101. Duringthis static relative spatial relationship between one of the testers 102and a corresponding one of the RFID devices 104 on the web 105, testingof that device may be performed. Thus sequential testing of the devices104 on the web 105 may be performed with a continuously moving web,without the need to move the testers 102 other than by rotating the testwheel 101.

The test system 100 may include components, such as supply and take uprolls for the web 105, and motors or other suitable devices for rotatingthe test wheel 101. The test modules (testers) 102 of the test wheel 101may be coupled to a suitable data concentrator at the hub of the testwheel 101. Data from the testers 102 and power for the testers 102 maybe provided across suitable connections between the test wheel 101 anddata-collecting and power-supplying devices outside the test wheel 101.Rotating joints or wireless links may provide suitable electricalconnection. Alternatively, information regarding test results for eachindividual device 104 may be passed to an appropriate data-gatheringdevice by suitable optical signals. For instance, the testers 102 may beconfigured to light one or both of a pair of indicator lights when atest is completed, indicating that the device 104 tested has passed thetest, failed the test, or that somehow the testing module failed toproperly perform the test. Suitable optical receivers may acquire thisinformation. Data about test results may be used to mark or removedevices 104 that failed testing.

The test wheel 101, with its large number of device testers 102, has theadvantage of being fault tolerant. Failure of a single tester 102results in a failure to test only a small fraction of the devices 104 onthe web 105. The system 100 may be configured to treat these untesteddevices 104 as devices that have failed their tests, without treating asubstantially large fraction of the devices 104 as failed test devices.

The test wheel 101 may be mounted in any of a number of suitableorientations, such as horizontally or vertically. It may have any of awide variety of suitable sizes, over which suitable numbers andconfigurations of RFID device testers 102 may be spread. In one example,the web 105 may have the devices 104 to be tested at a pitch of 50 mm.If the web 105 is to move at 3 m/s, in order to achieve 1 second of testtime the test wheel 101 must have a diameter of at least 1.9 m. Thusconfigured, the test wheel 101 would have 120 of the testers 102, with60 of the devices 104 on the web 105 being tested at any given time, andthe testing occurring at the rate of 60 devices per second.

It will be appreciated that the above numbers assume that the web 105extends over half (180 degrees) of the circumferential extent of thetest wheel 101. As shown in FIG. 10C, in an alternative embodiment thetest system 100 may have additional devices, such as auxiliary rollers106 and 107, to increase the amount of the test wheel 101 that is incontact with the web 105, for example bringing two-thirds or more of theperimeter of the test wheel 101 in contact with the web 105. By bringinga greater percentage of the perimeter of the test wheel 101 in contactwith the web 105, testing time may be increased, the size of the testwheel 101 may be reduced, and/or the speed of movement of the web 105and the test wheel 101 may be increased.

FIG. 10D shows another test system 100, which has multiple test modulesor testers 102 coupled to a belt 108 which engages and pulls along theweb 105 of RFID devices 104 to be tested. The elongate configuration ofthe belt 108 allows the web 105 to be in contact with a largerpercentage of the belt 108, achieving many of the same advantages as inthe configuration of FIG. 10C.

In FIGS. 11 and 12 embodiments of an RFID device test system 110 areshown. The RFID device test system 110 includes an RF tester 120 and atest fixture 124. The test fixture 124 includes shifting elements 126for shifting or changing the resonant frequency or optimum operatingfrequency of an RFID device 12 that is in close proximity to the testfixture 124. The shifting elements 126 may include dielectric elements128 a and 128 b (FIG. 11) for decreasing effective length of the antennaelements 36 and 38 of the RFID device 12. Alternatively, the shiftingelements 126 may include electrically-conducting elements 130 a and 130b (FIG. 12) for increasing effective length of the antenna elements 36and 38 of the RFID device 12. Thus the test fixture 124 may shift theresonant frequency or optimum operating frequency of the RFID device 12in a manner similar to that of the RFID devices testers 10 shown inFIGS. 4 and 5, and described above. This shifting of resonant frequencyor optimum operating frequency may be localized, and may besubstantially limited to a single RFID device 12 on a roll or sheet 134of RFID devices. Thus the test fixture 124 may enable RFID devices to betested singularly, despite their close proximity to othersubstantially-identical RFID devices.

The RF tester 120 may be a conventional RF reader for reading RFIDdevices through generation of a relatively long-range RF field, anddetection of changes in the RF field that occur due to the presence ofan RFID device within the field. Further information regarding suitableRF readers may be found in U.S. Pat. Nos. 5,621,199 and 6,172,609, bothof which are incorporated herein by reference in their entirety.

The RFID device 12 may be tested by having the RF reader 120 emit energyat a frequency corresponding to the shifted resonant frequency oroptimum operating frequency of the RFID device 12 in the test fixture124. Since this frequency is different from the natural resonantfrequency of other RFID device on the roll or sheet 134, substantialcoupling with the RF tester 120 may be confined to the single RFIDdevice 12 that is being tested. After testing, the sheet or roll 134 maybe shifted relative to the test fixture 124, allowing testing of anotherRFID device. Thus long-range non-capacitive coupling may be used tocouple to individual RFID devices on a sheet or roll of such devices.

It will be appreciated that the RFID device test systems 110 shown inFIGS. 11 and 12 may be modified, as suitable, in manners similar to thevarious modifications described for the RFID device testers 10. Forexample, the test fixture 124 may be incorporated into a roller, tofacilitate sing the RFID device test system 110 as part of aroll-to-roll process.

FIGS. 13 and 14 show one example of an RFID device test system 200 fortesting a web 202 of RFID devices or inlays 204. The test system 200includes a proximity sensor 210 for detecting the location of rows ofthe RFID devices 204 as the web 202 passed through the test system 200.The proximity sensor 210 may include one or more elements that detectthe presence of electrically-conductive material on the web 202, therebydetecting RFID devices 204.

The test system 200 also includes a number of testers 212 in a staggeredconfiguration, and a number of markers 214 for marking RFID devices 204that fail in testing. The testers 212 execute a performance test on eachof the RFID devices 204. The testers 212 may utilize capacitivecoupling, such as described above.

The staggering of the testers 212 allows sufficient separation to allowthe testing of individual RFID devices 204 without interference withoutbetween various of the testers 212. By placing the testers 212 in astaggered configuration, instead of next to one another in a row (forinstance), the testers 212 have increased distance from one another,facilitating their operative isolation from one another. In addition,the staggered configuration of the testers 212 may allow staggeredtiming of the testing by the various testers 212. With adjacent testers212 operating at different times, the possibility of interferencebetween adjacent testers is reduced, further enhancing the operativeisolation of the testers 212.

The proximity sensor 210 detects the leading edge of each row of theRFID devices 204. The proximity sensor 210 is operatively coupled to thetesters 212 to trigger, at appropriate times, the testers 212 to testthe RFID devices 204. The results of the testing by the testers 212 areutilized by the markers 214 to selectively mark some of the RFID devices204, for example by marking the RFID devices 204 that fail the testingby, for example, not demonstrating operation within acceptableparameters. The testing may include a qualitative test of the RFIDdevices or inlays 204. The markers 214 may include suitable ink jetmarkers.

FIG. 15 shows an example of the operative parts of the test system 200.The proximity sensor 210 and the testers 212 are operatively coupledtogether via a computer 220, such as a suitable personal computer,through the use of suitable input/output cards. The proximity sensor 210includes a pair of individual sensors 222 and 224 coupled to a proximitysensor card 226, which includes a proximity sensor power supply andproximity sensor input/output. The proximity sensors 222 and 224 may beKeyence ED-130U proximity sensors, wired together in the “and”configuration. Another example of a suitable proximity sensor is aproximity sensor available from Turck. The proximity sensor card 226 maybe a suitable RS-232 card.

The computer 220 may be any of a wide variety of suitable computingsystems capable of receiving and sending signals for controllingoperation of the test system 200. In addition to controlling operationsof the testers 212, the computer 220 may perform other functions, suchas recording the results of the testing, for example by maintaining alog of serial numbers of conforming RFID devices or inlays. The computer220 may be provided with suitable software to accomplish its purposes.

It will be appreciated that the computer may have any a wide variety ofdevices coupled thereto or a part thereof. For example, the computer 220may include a keyboard, mouse, or other device for allowing entry ofdata and/or allowing control of computer operations by a user. Thecomputer 220 may include a display showing, for example, status oftesting operations and/or results of testing.

The testers 212 include test dipoles 230 coupled to a suitable switch234, which in turn is coupled to the computer 220. Coaxial cables orother suitable conductors 236 may be used to coupled the test dipoles230 to the switch 234. The switch 234 controls timing of the testingutilizing the various testers 212, for example controlling the timing ofthe sending of the signals along the test dipoles 230, to capacitivelycouple the test dipoles 230 to the RFID devices 204. The computer 220uses information from the proximity sensor 210 to control the timing ofthe testing, in order to assure that the RFID devices 204 areappropriately located relative to the test dipoles 230 during thetesting, and to control the input to an RFID device reader 238.

The configuration shown in FIG. 15 allows coupling of multiple testdipoles 230 to the reader 238, allowing the testing of multiple RFIDdevices 204, in multiple columns, with a single reader. In FIG. 16,another possible configuration of the test system 200 is shown. In theconfiguration shown in FIG. 16, the device reader 238 has multipleinputs, so that it can be directly coupled to multiple dipoles 230.

The test system 200 may be capable of reading about 200 RFID devicesevery second, one RFID tag ever 5 ms.

FIG. 17 shows yet another configuration of the test system 200. Thesystem 200 includes a pair of computers 240 and 242, each coupled to arespective PCI card 244 and 246. The cards 244 and 246 are each coupledto multiple testers 212. A suitable choice for the testers 212 isavailable from Feig Electronic. The computers 240 and 242 are alsocoupled to respective proximity sensors 250 and 252.

FIG. 18 shows a timing diagram 300 for one possibility of timing of thesystem 200. The proximity sensor 210 registers an input 304 indicatingdetection of an inlay on the web 202. The sensor input 304 defines atest window 308. During the test window 308 the tester 200 performsvarious operations: a command 310 from the computer 220 to the reader238; transmission 314 from the reader 238 to one of the dipoles 230; aresponse 318 from the inlay of the RFID device 204; transmission 322 ofthe response from the reader 238 to the computer; and, if applicable,sending a signal from the computer 220 to the markers 214 for marking aRFID device that has failed a test.

Although the invention has been shown and described with respect to acertain embodiment or embodiments, it is obvious that equivalentalterations and modifications will occur to others skilled in the artupon the reading and understanding of this specification and the annexeddrawings. In particular regard to the various functions performed by theabove described elements (components, assemblies, devices, compositions,etc.), the terms (including a reference to a “means”) used to describesuch elements are intended to correspond, unless otherwise indicated, toany element which performs the specified function of the describedelement (i.e., that is functionally equivalent), even though notstructurally equivalent to the disclosed structure which performs thefunction in the herein illustrated exemplary embodiment or embodimentsof the invention. In addition, while a particular feature of theinvention may have been described above with respect to only one or moreof several illustrated embodiments, such feature may be combined withone or more other features of the other embodiments, as may be desiredand advantageous for any given or particular application.

1. A method of testing a plurality of radio frequency identification(RFID) devices, comprising: substantially continuously moving a web ofthat includes the RFID devices; at the same time, substantiallycontinuously moving at least a portion of a test apparatus that includesplural RFID device testers such that at least some of the RFID devicetesters maintain static relative spatial relationships with respectiveof the RFID devices for respective periods of time; and for each of theRFID devices, testing the RFID device with one of the RFID devicetesters while the RFID device is in a static spatial relationship withthe one of the RFID device testers.
 2. The method of claim 1, whereinthe device testers are placed along a perimeter of the test apparatus;and wherein the moving the at least a portion of the test apparatusincludes moving the device testers relative to other portions of thetest apparatus.
 3. The method of claim 2,wherein the moving the at leasta portion of the test apparatus includes rotating at least part of thetest apparatus.
 4. The method of claim 2,wherein the test apparatus iscircular, and the device testers are placed substantially evenly spacedabout the circumference of the test apparatus.
 5. The method of claim4,wherein the web is in contact with, and rotates with, part of thecircumferential extent of the test apparatus.
 6. The method of claim5,wherein the web is in contact with at least half of thecircumferential extent of the test apparatus.
 7. The method of claim5,wherein the web is in contact with at least two-thirds of thecircumferential extent of the test apparatus.
 8. The method of claim 2,wherein the RFID device testers are arrayed substantially evenly aboutan endless belt.
 9. The method of claim 8,wherein the belt is in contactand moves with the web.
 10. The method of claim 1, wherein the testingincludes: capacitively coupling the RFID device tester to an antenna ofthe RFID device; generating an outgoing signal from the RFID devicetester; using the outgoing signal to power the RFID device; generating areturn signal in the RFID device; and detecting a return signal, via areader that is part of the tester.
 11. The method of claim 1, whereinthe movement of the web is part of roll-to-roll process that involvesmoving the web from a supply roll to a take-up roll.
 12. The method ofclaim 1, wherein the movement of the web occurs at a rate of at least 3m/s.
 13. A method of testing a radio frequency identification (RFID)device, comprising: capacitively coupling an RFID device tester to anantenna of the RFID device; generating an outgoing signal from the RFIDdevice tester; using the outgoing signal to power the RFID device;generating a return signal in the RFID device; and detecting a returnsignal, via a reader that is part of the tester; wherein the RFID devicetester includes coupling elements electrically connected to the reader;wherein the antenna of the RFID device includes antenna elements;wherein the capacitively coupling includes aligning the couplingelements with respective of the antenna elements; wherein the couplingelements are part of a roller; wherein the RFID device is part of a rollmaterial; and wherein the aligning includes bringing the portion of theroll material having the RFID device into alignment with the couplingelements as the roller rotates.
 14. The method of claim 13, wherein thealigning is part of a roll-to-roll process.
 15. A radio frequencyidentification (RFID) device tester comprising: a reader; a pair ofelectrically-conductive coupling elements; a pair of transmission lineselectrically connecting respective of the coupling elements to thereader; and a resistor connected to both of the transmission lines,between the reader and the coupling elements; wherein the couplingelements are part of a roller.
 16. The device tester of claim 15,wherein the coupling elements are on an outer surface of the roller. 17.The device tester of claim 16, further comprising additional pairs ofcoupling elements on the outer surface of the roller, wherein theadditional pairs of coupling elements are also coupled to the reader.18. The device tester of claim 17, wherein the pairs of couplingelements are substantially evenly circumferentially spaced about theouter surface of the roller.